Essay on Ordinary men

This essay has a total of 1259 words and 7 pages.

Ordinary men

Samit Pabuwal
Jeff Toplak
EE 315
FUNCTION GENERATOR
12/12/2001

1.Abstract
This project requires us to design and build a circuit that generates specified functions
on the oscilloscope, as given on the project description. Also, we were required to design
a means of selecting different frequencies and different amplitudes. This was especially
difficult because the selection had to be made directly from the breadboard. For the final
part of the lab, we were to draw the graphs we obtained to show how the various functions
were generated digitally. The results we got were very sound. We were able to generate all
of the minimum requirements (a square wave and ramp wave). Also, we were able to generate
the waves that would give us extra credit (a triangle wave and approximations to a sine
wave). We also discovered a way to easily vary frequency and amplitude.


2.Introduction
This experiment uses four operational amplifiers (opamps) to deliver these waveforms in
the 6 Hz to 7000 Hz range. The sine wave is a pseudo sine wave produces by a very simple
wave

Shaping circuit. A digital counter can be used along with a DAC to generate analog voltage
functions of time such as square wave and ramp wave. In this lab, we were to design and
build a circuit that generates an analog square wave and a saw-tooth (ramp) wave of
voltage, using a counter and DAC/.


3. Design Process
While working on this project, we thought of alternatives that would increase efficiency.
An alternative we considered was to switch to a different project. This was thought about
when we were having trouble with the implementation of the circuit. However, we decided to
stick with this project. We decided this because we had already put in much thought and
work into this particular project. Also, we decided to use flip-flops to simplify the
circuit.


4. Implementation
CIRCUIT DESCRIPTION
Square, sine and triangle waves are produced using an LM348 and passive components. The
LM348 is a quad operational amplifier IC package; that is, it contains four separate
opamps all in the one IC. They are marked A, B, C & D in the schematic diagram.

Square Wave.
One opamp (LM348:D) is used. The voltage level to pin 13 is set by the resistor divider
pair R1 and R2. The input to pin 12 depends on two things; firstly the potential of

pin 14, and secondly, the voltage output of opamp C at pin 8. When the input at pin 13 is
higher than the input at pin 12 the output goes low. If it is lower then the output goes
high. Switching back and forth between the two states causes a square wave to be produced.
The time constant (R4 R5)C2 determines the frequency.

Triangle Wave.
You can also consider that opamp D is set up as a bi-directional threshold detector with positive feedback
provided by R3. R3 also gives hysteresis. The output provides a bias, which tends to keep
it in its existing state before allowing switching to take place. The inverting input is
set up at about half the opamp output swing voltage by resistors R1 andR2. Accordingly the
signal required from opamp C to cause switching is offset from this midpoint voltage by
R11/(R11 R3), which is approximately2/3 the voltage from midpoint to swing limit, and is
symmetrical above and below the switching point. Opamp C is set up as an integrator. It
performs the mathematical operation of integration with respect to time. For a constant
input the output is a constant multiplied by the elapsed time, that is, the output is a
ramp. Since the input signal goes to the inverting input, a high input will produce a ramp
down and a low input will produce a ramp up. The input signal is a square wave symmetrical
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